Press roll for papermaking machines



July 7, 1942. E.l E. BERRY v2158x515 l PRESS ROLL FOR PAPER MAKINGMACHNES -riiled May 29, 19:59

mental Juin, 1942 UNITED STATES. PATENT ori-"ICE f i l ansias PRESSVROLL FOR PAPERMAKING MACHINES nari s. Beloit, wa., signor to Beloit nongra, Beloit, Wis., a corporation of Wisconv application my 29, 1939,serial No. 216,377

comme (ci. :az-49) surfaces, when pressed against a wet paper web,

have a surface attraction for the web causing the same to tightly adherethereto. A pulling of the web oi'of such surfaces disrupts the surfacefiber formation of the web. The pulling force neces- Porous and openAccording to this invention press rolls are surfaced with relativelydense material having excel- 'lent wearing qualities but includingradial holes or perforations capable of trapping air therein as theyenter the nip of a press roll assembly. The trapped' air in the holes iscompressed as the holes pass through the nip of the p ress roll assemblyeither because'of' compression of the surface xnaterial defining theholes, or by entry of water from the wetiwebfipto the holes, or both.The compressed air in tile-holes;` immediately upon e out of the `nipaerea' of the press roll assembly, will blow the-weiifpd of .the rollsurface. thereby eliminating the heretofore encountered disadvantage inthe use of dense surfaced press' While rubber-covered perforatedsuctionrolls have heretofoebeen known, the perforations or holesextendin'gthrough the' rubber cover are aligned with holes in the metalsuction roll so that air cannot be entrapped. The present invention nowprovides for the sealing of holes extending radially inward from thesurface of the press roll at a point beneath the surface so that any airentering the holes from the surface of the roll will be trapped by asheet or web covering the .The press rolls of this invention preferablyinclude a metal cylinder covered with a layer of resilient material suchas rubber. The rubber layer, in turn; is covered with a perforatedrubber belt of denser construction" than the resilient rubber. Thisperforated rubber belt has excellent wearing qualities due to itsdensity and, if s desired, can be vulcanized to any hardnesspr'odoctored on the belt, air is trapped in and, when heat is applied tothe under surface of the-belt, the trapped air becomes hot and expands,blowing bubbles through the film of latex, thereby perforating the same.The perforated iilm is dried and the process repeated as many times asare required to build up a latex belt of the desired thickness. Thelatex material can be Y vulcanized to any hardnessdesired.

. It is, then, an object of this invention to provide a relatively densesurfaced press roll capable of repelling webs pressed thereagainst.

Another object of the invention is to provide a press roll surface`having blind holes extending inwardly therefrom to trap air as they area'dvanced into' the nip of a press roll assembly.

A further object of the invention is to provide a press roll coveredwith a perforatedrubber belt wherein the perforations are sealed beneaththe outer surface of the roll.

Anotherobject ofthe invention is to blow web material oil! of pressrolls by means of air trapped in the press roll surfaces during thepressing operation.

A further object of the invention is to compress air inthe circumferenceof a press roll for blowing a paper web off of said circumference.

Another object of the invention is to provide a pressroll covered with aresiliently backed per- A forated rubber belt.

Other and furtherv objects of the invention will become apparent tothose skilled in the art from the following detailed description of theannexedfl sheet of drawings.

On the drawing:

Figure 1 is a vertical cross-sectional`view illustrating, in somewhatdiagrammatic form, a twovlding some'ilexibility is retained. Small,uniformly arranged holes or perforations are formed through the belt andthese holes have well-defined fiat mouths at the surfacel of the belt soas A* present a flat, smooth surface for the rolls.

The perforated rubber surfaces of this invention can be made bydoctoring rubber latexon a pitted, heavy fabric belt. The surface of thebelt receiving the latex has uniformly spaced pits a top press Figure 3is a diagrammatic vertical cross-sec -tional view of a horizontal pressroll assemblyr including a press roll of this invention.

As shown` on the drawing: In Figures 1 and 2 'the reference numeral il idesignates generally a suction roll; As is cusvis mounted in thecylinder I I to define a--localized suction area.

A top press roll I5 cooperates with the suction roll IQ to define apressure nip receiving a web of paper W therethrough. The web W iscarriedon a felt VF. The pressure nip is preferably located soastobeinpartcommunicationwiththe localized suction area defined by thesuction box- Il.

therein closed at the bottom. -When the latex is no The top press rolll5, according to this inveneachpit'` tion, includes a metal cylinder I6,a layer of resilient rubber II covering the cylinder I6, and aperforated rubber belt I8 surrounding the rubber layer I1 and definingthe outer circumference of the roll. The rubber layer I1 can bevulcanized tothe cylinder I6 and rubber belt I8 and serves as a cushionbacking for the rubber belt.

As best illustrated in Figure 2, the rubber belt I8 has a plurality ofholes or perforations I9 extending therethrough. These holes I9 aresealed at the bottoms thereof by the rubber layer I1 so that theperipheral surface o f theroll I has a plurality of blind holesextending radially inwardly therefrom.

As illustrated in Figure 2, the rubber belt I8 is dense and relatively'incompressible as it passes through the niplarea. The rubber layer I1,however, is compressed at the nip area. 'I'he rolls Ill and I5 rotate inthe direction indicated by the arrows and air is wedged into the niparea. Some of this air becomes trapped in the holes I9 of the belt I8 asthe belt contacts the web W. This trapped air in the holes I9 vmayinitially be under slight compression due to the air wedge formed by therotating rolls. However, water pressed out of theweb W may also enterthe holes I9 as indicated at 28 to further compress with the web Wbefore they reach the nip area tact the web. This trapped air can befurther compressed by water squeezed into the holes from the web at thenip area, or, if desired, the rubber belt 34 can be slightly compressedat the nip area whereby the lengths of the holes will be decreasd tobringabout a further compression of the trapped air. As a result ofthese actions, the web W will be blown off of the belt 34 as soon as itpasses through the nip area. The web is then free to follow around thetop o'f the roll 38.

The rubber belts I8 and 34 are preferably formed by blowing air througha plastic material such as latex so as to create uniform small holesthrough the belts without damaging the flat `surfaces thereof. IWhilemechanically drilled rubber belts would be operative, the mouths of thedrilled bores would be rough and might damage the paper web. The mouthsof the sealedholes on the press rolls of this invention,

, however, are smooth and flat and the rolls have inch can be provided.

the trapped air in the holes. Immediately upony passage of the web outof the nip area, however, the trapped air is released and acts to blowthe web W off of the rubber belt I8 as indicated at 2|. If water hasbeen pressed into the holes I9,

the same will-be spewed out by the trapped air,

but will not have an undesirable effect -on the web W since the holesare preferably of minute sizeand cannot store appreciable amounts ofwater.,

. The top press roll I5 therefore operates to exert a desired pressureagainst the web W for squeezingwater out of the web but at the same timeits surface will not retain the web thereon as is customarywithheretofore known dense surfaced rolls. The web W therefore need notbe pulled away from the top press roll and its surface will not bedamaged.

If desired, the rubber belt I8 can be compressed at the nip area therebydecreasing the length of the holes I9 therein and thus increasing thepressure of the air trapped in the holes l In the horizontal press rollassembly disclosed in Figure 3, the reference numeral designates a metalcylinder in pressure relation with a press rodd 3| according to thisinvention. The cylinder 30 and the roll 3| have their axes in the samehorizontal plane so as to dene a vertical pressure nip therebetween. Aweb of paper W is trained around the under side of the roll 3| andpasses upwardlythrough the vertical pressure nip where it is subjectedto pressure for removal of water therefrom. g The removed water can dropby gravity out of the nip.

The roll 3| includes a metal cylinder 32, a resilient .rubber layer 33surrounding `the cylinder 32, and a perforated rubber belt 34 coveringthe rubber layer 33-to form the outer circumference for the roll. Theroll construction can be identical with the construction of the toppress roll I5 described in Figures 1 and 2. 'I'he perforations or holes35 in the rubber belt 34 are covered The perforated rubber beltspreferably have a very dense structure and will not become soggy duringuse as do belt or other fibrous covers for press rolls.

It will, of course, be understood, that various details of constructionmay be varied through a wide range without departing from the prinrubbercovering for said shell, and a perforated' relatively hard rubbercovering over the soft rubber in bonded relation thereto, said hardrubber covering presenting asmooth web-receiving surface on said rollwith a myriad of blind holes therein, said hard rubber covering beingcompressible to decrease the volumes of the holes when the covering issubjected to nip pressure.

2. In a press roll assembly including a suction roll, a press roll inpressure relation therewith defining a nip therebetween, means fordirecting a web of paper around said suction roll into said nip, asuction head in said suction roll defining a suction area extending intosaid nip. and means for rotating said rolls, the improvements whichcomprise said press roll having a perforated hard rubber coveringpresenting a web-receiving roll surface with a myriad of radiallyextending blind holes communicating with the atmosphere, and anunderlying resilient cushion bonded to and backing up the hard rubbercovering,.said

' rubber covering being compressible in said nip EARL E. BERRY.

